Then I would note that some sites prefer to contain the goddamn banners together with the rest of their "legitimate" images on their site, and they are only recognizable only by the slite they point to. Like:
<a href="nasty-commersial-url"><img src="seeme.gif"/> </a>

I think it would be very useful to block an image/object EITHER by the image url OR the "a href" that surrounds it (in my example "nasty-commersial-url").